XFS write speeds: software RAID 0/5/6 across 45 spindles

Wed, 02 Jan 2013 16:05:07 +0000

We’re currently building a new storage server to store low-priority data (tertiary backups, etc). One of the requirements for the project is that it needs to be on cheap storage (as opposed to expensive enterprise SAN/NAS). After some research we decided to build a Backblaze pod. Backblaze used 3TB Hitachi drives in their system, but the ones they listed in their blog post are discontinued and the reviews for all other 3TB+ drives were terrible, so we went with Samsung ST2000DL004 2TB 7200 RPM drives. Like Backblaze, we’re going with software raid, but I figured a good first step would be to figure out what RAID level we want to use, and if we want to use the mdadm/LVM mish-mosh Backblaze uses, or find something simpler. For my testing I created a RAID6 of all 45 drives and created a single XFS volume (XFS’s size limit is ~8 exabytes vs ext4’s 16TB). Ext4 may present some performance advantages, but the management overhead is probably not worth it in our case.

Problems with PostgreSQL 9.0 on CentOS 6.3 with a 2.6.32-series kernel

Tue, 25 Sep 2012 13:20:36 +0000

Note: this is cross-posted from the Yodle Tech Blog. We recently migrated our Postgres database to a significantly more powerful machine. While our existing server was doing okay load-wise, we were approaching 90% full on its Postgres volume. We’d also recently acquired an awesome new PureStorage SSD-based SAN and were excited to move our database onto it. For comparison, here are the the specs for the two systems:


	Old server	New server
Nickname	DB1	DB2
CPU	2x 6-core Xeon X5690 CPUs at 3.47GHz	2x 8-core E5-2690 CPUs at 2.90 GHz
Memory	96 GB 1333 MHz	128 GB 1600 MHz
Storage	- Dell PERC H800 SAS HBA - Dell MD1220 drive enclosure - 24x 15k RPM SAS drives configured in RAID 10	- QLogic QLE2562 dual-port 8 Gbit FC HBA - PureStorage SSD-based SAN
OS	CentOS 5.6 x86_64	CentOS 6.3 x86_64
Kernel	2.6.18-238.9.1.el5	2.6.32-279.2.1.el6.x86_64

As you can probably guess, moving from spinning disk onto SSD was the centerpiece of the upgrade. We’d tested the PureStorage system pretty extensively and used it in some secondary databases and seen some amazing improvements. We were excited to see how it would handle our production workload.

Hardware on Evan Hoffman

XFS write speeds: software RAID 0/5/6 across 45 spindles

Problems with PostgreSQL 9.0 on CentOS 6.3 with a 2.6.32-series kernel